From: Martin KaFai Lau kafai@fb.com
[ Upstream commit d623876646be119439999a229a2c3ce30fd197fb ]
By adding this test to test_verifier: { "reference tracking: access sk->src_ip4 (narrow load)", .insns = { BPF_SK_LOOKUP, BPF_MOV64_REG(BPF_REG_6, BPF_REG_0), BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 3), BPF_LDX_MEM(BPF_H, BPF_REG_2, BPF_REG_0, offsetof(struct bpf_sock, src_ip4) + 2), BPF_MOV64_REG(BPF_REG_1, BPF_REG_6), BPF_EMIT_CALL(BPF_FUNC_sk_release), BPF_EXIT_INSN(), }, .prog_type = BPF_PROG_TYPE_SCHED_CLS, .result = ACCEPT, },
The above test loads 2 bytes from sk->src_ip4 where sk is obtained by bpf_sk_lookup_tcp().
It hits an internal verifier error from convert_ctx_accesses(): [root@arch-fb-vm1 bpf]# ./test_verifier 665 665 Failed to load prog 'Invalid argument'! 0: (b7) r2 = 0 1: (63) *(u32 *)(r10 -8) = r2 2: (7b) *(u64 *)(r10 -16) = r2 3: (7b) *(u64 *)(r10 -24) = r2 4: (7b) *(u64 *)(r10 -32) = r2 5: (7b) *(u64 *)(r10 -40) = r2 6: (7b) *(u64 *)(r10 -48) = r2 7: (bf) r2 = r10 8: (07) r2 += -48 9: (b7) r3 = 36 10: (b7) r4 = 0 11: (b7) r5 = 0 12: (85) call bpf_sk_lookup_tcp#84 13: (bf) r6 = r0 14: (15) if r0 == 0x0 goto pc+3 R0=sock(id=1,off=0,imm=0) R6=sock(id=1,off=0,imm=0) R10=fp0,call_-1 fp-8=????0000 fp-16=0000mmmm fp-24=mmmmmmmm fp-32=mmmmmmmm fp-40=mmmmmmmm fp-48=mmmmmmmm refs=1 15: (69) r2 = *(u16 *)(r0 +26) 16: (bf) r1 = r6 17: (85) call bpf_sk_release#86 18: (95) exit
from 14 to 18: safe processed 20 insns (limit 131072), stack depth 48 bpf verifier is misconfigured Summary: 0 PASSED, 0 SKIPPED, 1 FAILED
The bpf_sock_is_valid_access() is expecting src_ip4 can be narrowly loaded (meaning load any 1 or 2 bytes of the src_ip4) by marking info->ctx_field_size. However, this marked ctx_field_size is not used. This patch fixes it.
Due to the recent refactoring in test_verifier, this new test will be added to the bpf-next branch (together with the bpf_tcp_sock patchset) to avoid merge conflict.
Fixes: c64b7983288e ("bpf: Add PTR_TO_SOCKET verifier type") Cc: Joe Stringer joe@wand.net.nz Signed-off-by: Martin KaFai Lau kafai@fb.com Acked-by: Joe Stringer joe@wand.net.nz Signed-off-by: Alexei Starovoitov ast@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/verifier.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 63a9253679f2..c0fb76d1e771 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1533,12 +1533,13 @@ static int check_flow_keys_access(struct bpf_verifier_env *env, int off, return 0; }
-static int check_sock_access(struct bpf_verifier_env *env, u32 regno, int off, - int size, enum bpf_access_type t) +static int check_sock_access(struct bpf_verifier_env *env, int insn_idx, + u32 regno, int off, int size, + enum bpf_access_type t) { struct bpf_reg_state *regs = cur_regs(env); struct bpf_reg_state *reg = ®s[regno]; - struct bpf_insn_access_aux info; + struct bpf_insn_access_aux info = {};
if (reg->smin_value < 0) { verbose(env, "R%d min value is negative, either use unsigned index or do a if (index >=0) check.\n", @@ -1552,6 +1553,8 @@ static int check_sock_access(struct bpf_verifier_env *env, u32 regno, int off, return -EACCES; }
+ env->insn_aux_data[insn_idx].ctx_field_size = info.ctx_field_size; + return 0; }
@@ -1948,7 +1951,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn verbose(env, "cannot write into socket\n"); return -EACCES; } - err = check_sock_access(env, regno, off, size, t); + err = check_sock_access(env, insn_idx, regno, off, size, t); if (!err && value_regno >= 0) mark_reg_unknown(env, regs, value_regno); } else {